This invention generally relates to self-closing caps for automotive fuel tanks, and is particularly concerned with a self-closing cap adapted for use with an automatic fuel filling machine.
Self-closing caps for automotive fuel tanks are well known in the prior art. Such caps allow a vehicle operator to fill the tank of his automobile or truck without the inconvenience of removing the gas cap from the filler neck. Such caps generally comprise a cap body with either screw threads or bayonet lugs for securing the cap body onto the open end of the filler neck of the car or truck gas tank. The cap body has a centrally disposed opening for receiving the nozzle of a gasoline or diesel fuel pump. This opening is normally covered by a spring biased closure flap that is pivotally connected to the cap body. A cover having finger indentations around its periphery and a centrally disposed opening aligned with the opening in the cap body is typically provided. In operation, the vehicle operator installs the self-closing cap in a conventional manner by screwing it over the filler neck of the fuel tank. To fill the tank the nozzle of a fuel pump is inserted through the opening in the cover and through the spring biased closure flap in the cap body. After the fuel tank has been filled, the nozzle is withdrawn and the spring in the cap body pivots the closure flap in its initial position against the nozzle receiving opening in sealing engagement. A particularly good example of such a prior art cap is disclosed and claimed in U.S. Pat. No. 4,986,439, the entire text of which is expressly incorporated herein by reference.
While these devices work well with conventional gas pumps where an operator manually operates a gas nozzle, the inventor has observed that such caps are poorly adapted for use with automatic fuel filling machines. Such machines include a robotic arm capable of moving both vertically and horizontally for aligning the nozzle of a gas pump with the filler neck of the truck or automobile. Such alignment is facilitated by the use of a magnetic position sensor in the robotic arm. After such alignment is completed, the robotic arm extends a gas nozzle toward the filler neck at an angle that is approximately orthogonal with respect to the vehicle wall surrounding the neck. The robot then extends the nozzle through the opening in the cap body and into the filler neck of the fuel tank by pushing down the pivotally mounted closure flap in the cap. In vehicles that run exclusively off of unleaded fuel, the fuel nozzle must also be extended through a second, pivotally mounted flap in the filler neck before the refueling operation can begin. The automatic filling machine then fills the tank through the nozzle and retracts the nozzle out of the filler neck and the cap in order to allow the restrictive flap in the neck and the closure flap in the cap to resume a closed position.
While roboticized fuel filling machines show great promise for the future, the applicant has observed three unfortunate incompatibilities between such machines and prior art self-closing gas cap designs. First, if the pivotal connection of the restrictive flap in the filler neck is not disposed approximately 180.degree. from the pivotal mounting of the closure flap, the nozzle of such roboticized fuel filling machines may not be aligned with the restrictive flap when the machine attempts to extend the nozzle into the filler neck. Secondly, even if the machine succeeds in extending the nozzle through both flaps, the nozzle may become jammed in the filler neck when the machine attempts to withdraw it. Either malfunction can result in damage to the self-closing cap or the fuel nozzle. Thirdly, because some filler necks are more obliquely than orthogonally oriented with respect to the adjacent sidewall of the truck or car to which they belong, the fuel nozzle of a roboticized filling machine can sometimes even fail to properly align with and extend through the closure flap of the self-closing cap.
Clearly, there is a need for a self-closing gas cap that can be consistently mounted at an angular position on the filler neck of a vehicle such that the pivotal connection of the restrictive flap in the neck of vehicles using unleaded fuel only is advantageously disposed 180.degree. away from the pivotal mounting between the closure flap and the body of the gas cap. Such a self-closing gas cap should further have some sort of provision for insuring that the nozzle of an automatic filling machine is smoothly and consistently received through the gas cap and into the filler neck even when the filler neck is not well aligned with the fuel nozzle of the automatic filling machine. It would be desirable if such a gas cap had an overpressure to prevent a rupture of the vehicle gas tank in the event of an accident. Finally, such a gas cap should be reliable in operation, relatively simple in structure, and easy and economical to manufacture.